One of my most vivid childhood memories is of a visit my Dad took my brothers and me on in 1964 to the Aransas Wildlife Refuge, near Corpus Christi in South Texas.  At one point during the tour, our tour guide stopped his Jeep in the middle of a grassy field and pointed to his left at a group of what appeared to be about 25 to 30 large, white birds who were feeding in a marsh.